The present invention relates to a developer reservoir of an electro-photographic copying machine and, more particularly, to a detection means for detecting the amount of developer powder contained in the developer reservoir.
There are various kinds of systems for detecting the amount of developer powder contained in the developer reservoir of an electro-photographic copying machine.
A typical example of an optical detection system is described in Japanese Patent Laid Open No. 50-34243, wherein a light beam impinges on a developing roller. A reflected light beam from the developer roller surface is detected by an opto-electric converter, of which an output level indicates the amount of developer powder carried on the developing roller. In this system, an accurate detection can not be ensured since the light emitting element and the light receiving element are positioned within the developer reservoir and they may be smudged by the developerpowder.
A typical example of a mechanical detection system is described in Japanese Utility Laid Open No. 50-50035, wherein a rotatable leaf is disposed within the developer reservoir. The inclination of the rotatable leaf indicates the amount of the developer powder contained in the developer reservoir. In this system, there is a possibility that the developer powder may preclude the preferred rotational operation of the rotatable leaf.
Other systems for detecting the amount of powder, for example, the electrostatic capacitance type and the torque variation detection type, are very complicated and, therefore, they are not suited for the electrophotographic copying machine wherein the consumption of a very little amount of powder should be detected.
Accordingly, an object of the present invention is to provide a detection means for detecting an amount of developer powder contained in a developer reservoir of an electrophotographic copying machine.
Another object of the present invention is to provide a developer powder detection device having a simple construction.
Still another object of the present invention is to provide a powder detection device which can detect the consumption of a small amount of powder.
Yet another object of the present invention is to provide an alarm system which activates an indication lamp when the developer powder contained in the developer reservoir becomes less than a predetermined amount.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, an opening is formed in a bottom wall of a developer reservoir, where a U-shaped diaphragm is secured. The diaphragm is bent downward when developer powder is present in the developer reservoir in more than a predetermined amount. When the quantity of developer powder decreases to below the predetermined amount during the development operation, the diaphagm returns to its initial shape, that is, the diaphagm is bent upward. The bent condition of the U-shaped diaphagm is detected through the use of a suitable detection means such as a microswitch, whereby an alarm lamp is activated when the developer powder decreases to below the predetermined amount.